Flashlight lamp



April 6, 1948. J. H. DE BQER 2,438,993

FLASHLIGHT LAMP Filed March 20, 1944 FIG- 5 JAN HENDRIK DE BOER INVENTOR ATTORNEY ing tted at each end oi each tube.

Patented Apr. 6, 1948 Y rLAsuucn'r LAMP Jan Hendrik de Boer, London, England,`assignor to The Hartford National Bank and Trust Company, Hartford, Conn., as trustee 'Application March 20, 1944, Serial No. 527,284

In Great Britain Januaryv, 1943 sehnen 1, Public Lew 69o, August s, 194s Patent expires January 8, 1.963

e claims. (c1. ven -*31) Proposals have been made to replace the conventional'glass envelope of photographic flashlight lamps by an envelope of 'transparent or translucent organic material, such as cellulose and cellulose derivatives. In such flashlight lamps one of the chief problems is to achieve perfect gas-tightness at all`points, as any diffusion through the envelope or leaks in the envelope lead not only to a change in the pressure of the gaseous filling but also in general to a change in the composition thereof.

Diilusion ci gas through the wall of the envelope can be avoided by the use of an envelope formed of at least two layers, one consisting of regenerated cellulose as described and claimed in the specification of application for Patent Serial No. 475,952 now U. S. Patent No. 2,325,667 issued August 3, 1943. The present invention has for its object to prevent leaks at points where componente of the flashlight lamp have to form a seal. While the present invention can be used `with particular advantage in combination with the invention of specification Serial No. 475,952 it is not limited to such combination.

The points where the components have to make a seal arise from the provision of the lead-in conductors.

These lead-in conductors may pass directly through the envelope in which case there is a direct' seal between them and the envelope, or they may pass through or be constituted by parts oi a base which has to lbe sealed to the envelope, in which case thereis an indirect seal between the lead-in conductors and the envelope.

According to one aspect of the present invention, in the former of the above-mentioned two cases, the lead-in conductors are encased in a sheath of regenerated cellulose and this sheath is sealed into the envelopev of organic material. The lead-in conductorsmay advantageously be dat metal strips, preferably with a matt or sand blasted surface. The strips and the encasing sheath oi' regenerated cellulose may be corrugated in order to increase the length of the seal. As an alternative to the use of solid lead-in conductors, use may be made of a conducting Jelly contained in small bore tubes of regenerated cellulose passing through and sealed into the envelope, connecting wires be- The conducting jelly may consist of a solution of a suitable salt such as potassium chloride, sodium sulphate, sodium phosphate, sodium nitrate, or a suitable acid or alkali, made up into a gel with a few percent of gelatin or agar-agarwith the addition of a few drops of preservative to prevent mould growth. Another form of lead-in conductor is rubber impregnated with graphite (25% to 30% of graphite) which is electrically conducting, can readily be prepared in a strip form, and gives a' satisfactory seal with regenerated cellulose.

In the case 4of two-part envelopes comprising a translucent or transparent body portion and a base portion, comprising the lead-in conductors as in the latter of the above-mentioned two cases, a satisfactory hermetic seal can be produced by using an Ebonite base and a cellulosic envelope. The base may be made in part of ordinary Ebonite and in part of graphite-impregnated elec`V trically-conducting Ebonite. If two separate parts of electrically conductingEbonite are provided they can serve as the lead-in conductors. but if only one such part is provided the other lead-in conductor can take the form of a' metal wire sealed into and passing through the non-` conducting Ebonite.

In order that the invention may be more readily understood reference will now be had to the accompanying diagrammatic drawings in which:

Figs. l to 3 show corresponding central sections through three different constructions according to the invention.

Fig. e is a fragmentary section on a larger scale showing another feature of the invention.

Fig. 5 is a section along lthe line 'lil-V of Fig. 4.

In the embodiment of Fig. l, the photographic flash-lamp comprises a transparent envelope and a non-transparent base. The envelope consists of two layers; an outer layer t of a transparent organic material, such as non-inflammable cellulosic material, which exhibits some elasticity and preferably some flexibility, for instance cellulose acetate, polyvinyl chloride, urea formaldehyde resin, polyacrylicacid or ethers, polyvinyl ethers; and an inner layer of regenerated cellulose. The base 3 consists of a disc of electrically conducting Ebonite which is sealed. to the envelope layer 2. The base 3 has an externally projecting ring 4 serving for electrical connection to one pole of the source of current tor the @lament 8. Sealed in the conducting Ebonite base d is a plug 5 of non-conducting Ebonite through which passes a lead-in conductor which is i'or connection to the other pole or" the source. Within theenvelope, the iilament t is mounted between the conductor G and a wire 'l secured in a blind hole in the base 3. The envelope contains the usual filling of combustible material such as thin wire or foil of aluminiwn or aluminiummagnesium alloys. It also contains a combustion-supporting gas and may also contain solid substances which under the conditions of the reaction evolve a gas which supports the com.-

bustion.

In the embodiment oi' Fig. 2, the envelope consists of three layers, viz. layers l and 2 as in Fig. 1 and a layer 9 similar to layer i. In this case, the base consists o a disc i of non-conducting Ebonite, in which are incorporated two plugs il, I2 of conducting Ebonite. The iilament 3 is carried by pins I3, It secured in blind holes in the inner ends of the plugs il, i2,

In Fig. 3, the envelope i consists of a transparent non-inammable cellulosic material such as constitutes the envelope i of Figs. 1 and 2 and is sealed to a similar disc it. The electrical leadin arrangements consist of two tubes il, i3 of cellulosic material, preferably regenerated cellulose, rllled with a conducting lpaste or jelly as indicated at 2l, 22; lead-in Wires i3, 2@ and Lillament supporting wires 23, 2Q are sealed in at the ends of the tubes il, i3. The tubes il, i3 themselves are sealed in the envelope i5. `vits in the embodiments described with reference to Figs. 1

and 2, the wires, 23, 2li both support and carry,

current to the filament 3. It will be apparent that this lead-in arrangement could be utilised with envelopes constructed in accordance with either Fig. 1 or Fig. 2. Moreover, the base and lead-in arrangements of either Fig. l or Fig. 2 could be used with a single layer envelope of the kind shown in Fig. 3.

In Figs. 4 and 5, 2l represents a wall portion through which the lead-in wires are to be sealed. To ensure a goed seal, the lead-in conductors 25, 23 are each encased in a sheath of regenerated cellulose 29, 36, which sheath is sealed to the wall 2. Preferably the ends of the sheaths 23, 3@

are sealed to a sealing layer 23 of regenerated cellulose associated with the wall 2l. The conductors 25, 2t are preferably of strip form as shown in Figs. 4 and 5 and may consist of metal or of electrically conducting graphite-impregnated rubber. advantageously that part of each of the conductors 25, 2S which is embedded in the wall 2l' is corrugated as shown in Fig. 4 to increase the effective length of the seal Without increasing the over-all dimensions. When metal conductors are used, the surface may be sandblasted or otherwise rendered matt'to improve the adhesion thereto of the regenerated cellulose sheath.

I claim:

l. A ash lamp comprising a container having an envelope portion of transparent organic material, combustible material and a combustionsupporting gas within the container, means for igniting the combustible material, non-metallic electrical lead-in conductor constituting part of another portion of the container. and a sealing layer of regenerated cellulose interposed between said container portions.

2. A ash lamp comprising a container having 4 an envelope portion of transparent organic material, a combustible material and a combustionsupporting gas Within the container, means for igniting the combustible material, a lead-in conductor of electrically conducting organic material constituting part of another portion of the container, and a sealing layer` of regenerated cellulose interposed between said container portions.

3. A flash lamp comprising a container having an envelope o1 a transparent organic material, a base of an electrically conductive organic material having a central portion thereof of an electrically insulating organic material, a sealing layer of regenerated cellulose interposed between the envelope and the base, a combustible material and a combustion-supporting gas within the container, means for ignitlng the combustible material, and a lead-in conductor sealed through said electrical insulating central portion of the base.

4. A flash lamp comprising a container having an envelope lcomprising a layer of a transparent organic material, a base of an electrically conductive organic material having a central portion thereof of an electrically insulating organic material, a sealing layer of regenerated cellulose covering said layer of transparent organic material and interposed between the same and the base, a combustible material and a combustionsupporting gas Within the envelope, and a leadin conductor sealed through said electrically insulating central portion of the base.

5. A flash lamp comprising a container having an envelope of a transparent organic material, a base of an electrically insulating organic material, a sealing layer of regenerated cellulose interposed between the envelope and the base, a combustible material and a combustion-supporting gas in the container, means for igniting the combustible material, and lead-in conductors of electrically conducting organic material passing through and sealed to said base.

6. A ash lamp comprising a container having an envelope of a transparent organic material, a base of organic material, a combustible material and a combustion-supporting gas in the container, means for igniting the combustible material, lead-in conductors consisting of a conducting jelly interposed between the base and the envelope, and tubular layers of regenerated cellulose enclosing the lead-in conductors and sealed to the envelope and the base.

REFERENCES CHIEDI) The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,305,609 Eaton Dec. 22, 1942 2,325,667 De Boer Aug. 3, 1943 2,333,725 Kreidler Nov. 9, 1943 

